Assessment of Biogas Yield Potential Based on Physicochemical and Biodegradability Characteristics of Mushroom Substrates

Abstract

The growing global demand for sustainable and renewable energy has underscored the significance of biogas as an alternative to fossil fuels. This study evaluates the biogas production potential of four organic substrates: Button mushroom spent substrate (BMS), Oyster mushroom spent substrate (OMS), Wheat compost (WC) and Paddy compost (PC), with a focus on their physicochemical and biochemical characteristics. Standard protocols (APHA, 2022) were employed to analyze parameters including total solids (TS), volatile solids (VS), pH, alkalinity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrogen (N), phosphorus (P), potassium (K) and organic carbon (C). Results revealed that BMS and OMS had superior nutrient profiles with higher concentrations of N, P and K and favourable C:N ratios of 32.6:1 and 34.2:1 respectively, within the ideal range for anaerobic digestion. BMS showed the highest BOD (1024.3 mgL-1) and COD (2976.67 mgL-1), indicating high biodegradability and methane-generating potential. OMS exhibited the highest VS (66.83%) and VS/TS ratio (0.77), suggesting an abundant fraction of biodegradable organic matter. Although PC displayed the highest carbon content (32.98%), its high C:N ratio (57:1) indicated nitrogen deficiency and poor microbial degradation potential unless co-digested with nitrogen-rich substrates. WC and PC also demonstrated higher alkalinity but lower overall biogas potential. Statistical analysis (One-way ANOVA, Tukey b test, P≤0.05 confirmed significant differences among substrates in key parameters influencing biogas yield. In conclusion, BMS emerged as the most promising substrate for biogas production, owing to its balanced pH, high organic load and ideal nutrient composition. OMS also showed excellent potential but may require pH correction or co-digestion strategies. Further research on kinetic modelling and reactor-scale validation is required to optimize substrate mixtures and improve energy recovery efficiency in anaerobic digesters.